This proposal describes 2 studies designed to prospectively evaluate some basic parameters of outpatient substance abuse treatment and determine if these parameters influence treatment effectiveness. Study 1 compares three different treatment episode "Doses" of outpatient treatment. Durations of 4, 8, and 16 weeks are the 3 treatment episode "doses" compared. Protocols for each of the 3 episode "doses" will involve 3, 90-minute sessions per week and will include the same content material delivered in a manualized group treatment approach. Study 2 investigates the importance of the size and frequency of each group session "dose" of content material when delivered in a 12 week manualized protocol. In study 2, size of "dose" is assessed by comparing the effect of group sessions of 50 minutes and 150 minutes. In addition, the importance of frequency of "dose" is assessed by comparing 1 session per week with 3 sessions per week. This study uses a 2x2 design such that the impact of both variables (size and frequency) and their interaction (size x frequency) can be evaluated. A battery of data will be collected in both studies to assess the impact of treatment delivery parameters on: retention in treatment; stimulant use during treatment; other drug and alcohol use during treatment; psychosocial behavior change during treatment (ASI and BASIS-32); HIV-related risk behaviors (NIDA/AIDS); and 6 and 12 month evaluations to assess the long term effect of the study variables. In both studies, SCID diagnostic evaluations will be completed on all Ss.